Pallets are used frequently in shipping goods and are normally constructed of an upper tier of deck panels. More specifically, a typical pallet is constructed by nailing a series of deck panels to a supporting base. The deck panels form a load support surface upon which goods to be transported are placed.
Such pallets are generally of two types: block-type P1 and stringer-type P2 pallets. A representative stringer-type configuration is seen in accompanying FIG. 1D. The stringer-type pallet P2 includes three-spaced, parallel support members along the pallet length to which upper, and possibly lower deck panels are nailed perpendicular or widthwise. Stringer-type pallets utilize rectangular stringers or runners that run the full length of the pallet. The top-deck is fastened to the upper-most surface or top of the stringers. For double-face pallets, the bottom deck is fastened to the bottom surface of the stringers. Since the height of the rectangular stringers are three inches or more, top-deck panels are typically fastened very securely to the stringer using relatively long nails.
A standard block-type pallet P1, on the other hand, employs a number of relatively small, rectangular-spaced blocks onto which three-spaced, parallel stringer boards, typically about ¾th-inch thick, are attached lengthwise. A representative block-type configuration is seen in accompanying FIG. 1A. Upper and lower deck panels are fastened, typically nailed perpendicular to the aforementioned stringer boards widthwise to the pallet proper. The upper deck panels are generally indexed T1 through T4 from front or lead-end to the rear-most pallet end, i.e. along the pallet length. Specifically, the lead top-deck panel is identified as T1. The next panel in sequence is T2, followed by two T3 deck panels, then a T4 panel positioned over the three center blocks, two perimeter center blocks B2 and one in the middle or center of the pallet BC. Continuing in sequential order, there are two more T3 panels followed by another T2 and finally, another T1 panel at the rear-most pallet end. It is important to note that the lead and rear-most T1 panels of each block-type pallet are positioned over the end blocks B1 at each pallet corner and a center block B2 therebetween. The adjacent T2 panels are divided with about half of each panel width positioned over the same end blocks as their neighboring T1 panel. In many instances, the T1 and T2 panels are in direct abutting contact along the pallet width. The T3 panels, by contrast, only fasten to the thinner stringer boards SL, SM and SR between pallet end and center blocks. For structural strength, T1 and T4 panels are usually made from hardwood, such as red or white oak for structural strength, while T2 and T3 panels are typically cut from a soft pine. As a result, the T3 deck panels are more prone to work their way loose over time due to the softer wood and shorter nails used to attach the same to the thinner stringer boards.
Also, it is important to note that the spaces between blocks and stringer boards of a block-type pallet P1 or between stringers of a stringer-type pallet P2 are adapted to receive the tines of conventional forklift trucks. In the course of being moved from place to place with the forklift, these pallets become damaged. Particularly, T1 panels are often hit with the nose of the forks. Although T1 panels are usually made from harder wood, after repeated use, the nails used to fasten the T1 deck panels work loose, particularly if improperly lifted. Also, T1 panels are more prone to be partially or completely broke if the forks are not properly positioned before lifting. If these problems are not corrected, the random, upstanding nails and broken panels will damage the goods loaded and/or removed from these pallets. Although the difference in board thicknesses and nail-to-board height difference may seem relatively small, it often causes substantial property damage and loss by tearing or scratching the packaging, goods and/or equipment stacked on the pallet.
As a result of its configuration and construction, during repair or furbishing of block-type pallets P2, a problem often arises if a T1, or even T4 panel is replaced with a board not fully cured. Specifically, the width of the T1 panel is about ¾th-inch thick when freshly cut. After curing, that same panel typically shrinks in thickness to about 11/16th-inch. Therefore, if a T1 panel is replaced with another not fully cured, it is often slightly thicker than the other deck panels. Also, a replacement panel may be accidentally cut thicker or thinner than standard board thicknesses. Whatever the reason, it has been found that this replacement board-thickness difference often causes a serious problem. That replacement board thickness difference is shown, for example, by spacing d2 in accompanying FIG. 1C. Also note, FIG. 1C shows a nail that has worked loose and extends above the pallet surface prior to pressing according to the invention. The nail-above-board spacing is shown as d1.
While more pronounced with block-type pallets, the problem of raised or extended fasteners and replacement board thickness differences also occurs with stringer-type pallets.
When pallets having the problems described are being furbished and passed through a pallet nail press such as that described in U.S. Pat. No. 5,375,315, the top anvil may hit the top surface of each T1 and T4 panels, but, if a T1 panel, for example, is thicker than the other deck panels for the reasons stated, that same anvil will never completely contact the top surface of adjacent, and relatively lower, T2 and T3 panels. Since they are made of hardwood, these T1 and T4 panels are less forgiving and compress only slightly as compared to the adjacent T2 and T3 panels made from relatively softer woods. As a result, nails extending above the surface of the thinner panels are not rendered flush with the pallet top surface, as should be the case after passing through the nail press. Also, if one of the stringer boards SL, SM or SR is slightly bowed downward between blocks, a new replacement T1 or T4 panel may extend even higher above its nearby T2 and T3 panels, further exacerbating the problem of varying nail heights above the pallet top surface after compression with a nail press.
Notably, with existing, automated pallet nail presses, it is difficult to adjust the compression force in the press to contact these lower areas across the pallet upper surface. If too much compression is applied to force complete press-to-pallet contact, damage to the thicker areas of the pallet and/or blocks therebeneath occurs.
In the field of pallet manufacturing, automation is known, as seen for example in the automatic apparatus and methods of Buck U.S. Pat. Nos. 6,736,591 and 6,430,800, or the earlier apparatus of Pope's U.S. Pat. No. 5,555,617. There are also known methods and equipment for removing components to pallets such as the board and stringer removal apparatus of Minick's U.S. Pat. No. 6,829,822 and Beane's U.S. Pat. No. 6,032,351. For lumber related applications, Runnebaum's U.S. Pat. No. 5,547,002 discloses a variety of framed press machinery. And, in a completely different context, Ilies' U.S. Pat. No. 6,763,564 teaches a method and apparatus for driving fasteners into an electric fan assembly. But, none of the foregoing addressed automating pallet furbishing, particularly the driving of fasteners into block-type pallet upper surfaces, as well as their stringer design counterparts having a less than planar top or uppermost surface.
For these and other reasons, it is an objective of this invention to address the aforementioned pallet repair shortcomings and provide a more universal, dynamic nail press and method that will accommodate varying panel thicknesses, bowing, warping, and other imperfections for pressing down all fasteners that otherwise extend above its uppermost surface. The preferred press described herein for embedding outwardly extended or loosened nails and other fasteners, includes a press having an anvil with a plurality of anvil plates resiliently attached to a frame with a hammer beam movably positioned in a vertical space alignment with the several anvil plates. A drive is used for advancing the hammer beam sufficiently away from a conveyor system and preferably toward the anvil plates for compressing the top-deck panels therebetween to more completely embed into the pallet upper panels any extended fasteners. Alternately, if the pallet is sufficiently separated from the underlying conveyor, the resiliently attached anvil plates can be lowered down and over the pallet proper for embedding any and all raised fasteners from the pallet's uppermost surface.
For this and other reasons, this invention represents a significant advantage over other automated machines, even the pallet nail press and method of Griffith, et al., U.S. Pat. No. 5,375,315.